The present invention relates to a pressure core barrel assembly for recovering a core at formation pressure and is specifically directed to improvements in the type of pressure core barrel described in U.S. Pat. No. 3,548,958 issued 12/27/70 to Blackwell and Rumble. In such a pressure core barrel assembly it is important to know that the pressure core barrel has been sealed at formation pressure before the barrel is raised to the surface. If it is not sealed the sample will not be representative of the actual conditions existing in the formation at the bottom of the well.